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PubMed1994

The search for other planets: clues from the solar system.

Studies of element abundances and values of D/H in the atmospheres of the outer planets and Titan support a two-step model for the formation of these bodies. This model suggests that the dimensions of Uranus provide a good index for the sensitivity required to detect planets around other stars. The high proportion of N2 on the surfaces of Pluto and Triton indicates that this gas was the dominant reservoir of nitrogen in the early solar nebula. It should also be abundant on pristine comets. There is evidence that some of these comets may well have brought a large store of volatiles to the inner planets, while others were falling into the sun. In other systems, icy planetesimals falling into stars should reveal themselves through high values of D/H.

Astronomical Phenomena↗

PubMedDate not supplied

Experimental simulation of Titan's organic chemistry at low temperature.

A wide range of experiments has already been carried out to simulate the chemical evolution of Titan. Such experiments can provide useful information on the possible nature of minor constituents, mostly organic, likely to be present in Titan's atmosphere. Indeed, all but one of the organic compounds already detected in Titan's atmosphere have been identified in simulation experiments. The exception, C4N2, as well as other compounds expected in Titan from theoretical modeling, such as other N-organics, mainly CH2N2, and polyynes, namely C6H2, have never been detected in experimental simulation. It turned out that these compounds were thermally unstable, and the temperature conditions used during the simulation experiments (including conditions used for chemical analysis) were not appropriate. We have recently started a new program of simulation experiments using temperature conditions close to those of Titan's environment, more compatible with the build-up and detection of organics only stable at low temperature. Spark discharge of N2-CH4 gas mixtures was carried out at low temperature in the range of 100-150 K. The analysis of the obtained products was performed through FTIR, GC and GC-MS techniques. GC-peak identification was done owing to its mass spectrum and, in most cases, by comparison of the retention time and of the mass spectrum with standards. We report here the first detection in Titan's simulation experiments of C6H2. Its abundance is a few 10(-2) relative to C4H2. We also report a tentative identification of HC5N (to be confirmed by use of standard) with an abundance of a few 10(-2) relative to HC3N. The possible presence of HC5N suggested by our work provides the occurrence of very novel pathways in the formation of Titan's organic aerosols, involving not only C and H but also N atoms.

Acetylene↗

PubMed2005

Composition and structure of the 80S ribosome from the green alga Chlamydomonas reinhardtii: 80S ribosomes are conserved in plants and animals.

We have conducted a proteomic analysis of the 80S cytosolic ribosome from the eukaryotic green alga Chlamydomonas reinhardtii, and accompany this with a cryo-electron microscopy structure of the ribosome. Proteins homologous to all but one rat 40S subunit protein, including a homolog of RACK1, and all but three rat 60S subunit proteins were identified as components of the C. reinhardtii ribosome. Expressed Sequence Tag (EST) evidence and annotation of the completed C. reinhardtii genome identified genes for each of the four proteins not identified by proteomic analysis, showing that algae potentially have a complete set of orthologs to mammalian 80S ribosomal proteins. Presented at 25A, the algal 80S ribosome is very similar in structure to the yeast 80S ribosome, with only minor distinguishable differences. These data show that, although separated by billions of years of evolution, cytosolic ribosomes from photosynthetic organisms are highly conserved with their yeast and animal counterparts.

Algal Proteins↗

PubMed2006

Determination of paracetamol: historical evolution.

Paracetamol is a common analgesic and antipyretic drug that is used for the relief of fever, headaches and other minor aches and pains. Their determination in pharmaceuticals is of paramount importance, since an overdose of paracetamol can cause fulminating hepatic necrosis and other toxic effects. Many analytical methodologies have been proposed for the determination of paracetamol. The aim of the present study is to evaluate the utility of different techniques for quantification of paracetamol content in pharmaceutical formulations and biological samples.

Acetaminophen↗

PubMed1993

Extinction from a paleontological perspective.

Extinction of widespread species is common in evolutionary time (millions of years) but rare in ecological time (hundreds or thousands of years). In the fossil record, there appears to be a smooth continuum between background and mass extinction; and the clustering of extinctions at mass extinctions cannot be explained by the chance coincidence of independent events. Although some extinction is selective, much is apparently random in that survivors have no recognizable superiority over victims. Extinction certainly plays an important role in evolution, but whether it is constructive or destructive has not yet been determined.

Adaptation, Biological↗

PubMed1989

Annihilation of ecosystems by large asteroid impacts on the early Earth.

Large asteroid impacts produced globally lethal conditions by evaporating large volumes of ocean water on the early Earth. The Earth may have been continuously habitable by ecosystems that did not depend on photosynthesis as early as 4.44 Gyr BP (before present). Only a brief interval after 3.8 Gyr exists between the time when obligate photosynthetic organisms could continuously evolve and the time when the palaeontological record indicates highly evolved photosynthetic ecosystems.

Biological Evolution↗

PubMed2006

The origin and emergence of life under impact bombardment.

Craters formed by asteroids and comets offer a number of possibilities as sites for prebiotic chemistry, and they invite a literal application of Darwin's 'warm little pond'. Some of these attributes, such as prolonged circulation of heated water, are found in deep-ocean hydrothermal vent systems, previously proposed as sites for prebiotic chemistry. However, impact craters host important characteristics in a single location, which include the formation of diverse metal sulphides, clays and zeolites as secondary hydrothermal minerals (which can act as templates or catalysts for prebiotic syntheses), fracturing of rock during impact (creating a large surface area for reactions), the delivery of iron in the case of the impact of iron-containing meteorites (which might itself act as a substrate for prebiotic reactions), diverse impact energies resulting in different rates of hydrothermal cooling and thus organic syntheses, and the indiscriminate nature of impacts into every available lithology-generating large numbers of 'experiments' in the origin of life. Following the evolution of life, craters provide cryptoendolithic and chasmoendolithic habitats, particularly in non-sedimentary lithologies, where limited pore space would otherwise restrict colonization. In impact melt sheets, shattered, mixed rocks ultimately provided diverse geochemical gradients, which in present-day craters support the growth of microbial communities.

Biological Evolution↗

PubMed2006

Electric-field-induced domain evolution in ferroelectric ultrathin films.

The electric-field-induced evolution of the recently discovered periodic 180 degree nanostripe domain structure is predicted in epitaxial Pb(Zr0.5Ti0.5)O3 ultrathin films from first principles. This evolution involves (1) the lateral growth of majority dipole domains at the expense of minority domains with the overall stripe periodicity remaining unchanged, (2) the creation of surface-avoiding nanobubbles, and (3) the formation of a single monodomain state. Analogies and differences (i) with ferroelectric thin films made of BaTiO3 and (ii) with ferromagnetic thin films under magnetic field are discussed.

Journal Article↗

PubMed2003

Evolution of planetary cores and the Earth-Moon system from Nb/Ta systematics.

It has been assumed that Nb and Ta are not fractionated during differentiation processes on terrestrial planets and that both elements are lithophile. High-precision measurements of Nb/Ta and Zr/Hf reveal that Nb is moderately siderophile at high pressures. Nb/Ta values in the bulk silicate Earth (14.0 +/- 0.3) and the Moon (17.0 +/- 0.8) are below the chondritic ratio of 19.9 +/- 0.6, in contrast to Mars and asteroids. The lunar Nb/Ta constrains the mass fraction of impactor material in the Moon to less than 65%. Moreover, the Moon-forming impact can be linked in time with the final core-mantle equilibration on Earth 4.533 billion years ago.

Earth, Planet↗

PubMed1976

Chromosome banding pattern relationships of hares, rabbits, and pikas (order Lagomorpha). A phyletic interpretation.

The chromosome banding patterns of the domestic rabbit, Oryctolagus cuniculus, the brush rabbit, Sylvilagus bachmani, and the snowshoe hare, Lepus americanus, are nearly identical except for minor differences in the amount of constitutive heterochromatin present. The major mechanisms of chromosome evolution in leporid lagomorphs are centric fusion and addition of heterochromatin. The G- and C-banding patterns of the pika, Ochotona princeps, revealed little easily recognized structural homology with the leporid species. Several tentative banding pattern matches were found for segments of some chromosomes of Ochotona, indicating that tandem fusions may have been responsible for structural modification of the early lagomorph genome. Chromosome evolution in the lagomorphs and the use of chromosomal data in studies of mammalian systematics are discussed.

Animals↗

PubMed1996

Relative position and extent of the nasal and orbital openings in Gorilla, Pan and the human species from the study of their areas and centres of area.

In order to quantify the relative position and extent of the nasal and orbital openings in hominoid primates, a new methodology based on image analysis was developed and applied to a series of 134 hominoid skulls (52 Gorilla gorilla; 30 Pan troglodytes; 44 Homo sapiens, and, as comparison material, 8 Pongo pygmaeus). The areas and the centres of area of the orbital and nasal openings were determined automatically. The orbitonasal triangle connecting these three centres of area was then constructed. This triangle was used to quantify the elongation of the face. It was most elongated in gorilla, shortest in the human species and intermediate in Pan; the elongation in Pongo was close to that in Gorilla. The proportions of the areas of the orbital and nasal openings in the face were related to the extent of the bony structures of the midface and were thus used to quantify the facial robustness. A robust face was demonstrated in Gorilla, but a gracile face in the human species. Robusticity in Pan was intermediate.

Anatomy, Comparative↗

PubMed2005

Chromosomal mapping of quantitative trait loci controlling elastin content in rat aorta.

Extracellular matrix molecules such as elastin and collagens provide mechanical support to the vessel wall. In addition to its structural role, elastin is a regulator that maintains homeostasis through biologic signaling. Genetically determined minor modifications in elastin and collagen in the aorta could influence the onset and evolution of arterial pathology, such as hypertension and its complications. We previously demonstrated that the inbred Brown Norway (BN) rat shows an aortic elastin deficit in both abdominal and thoracic segments, partly because of a decrease in tropoelastin synthesis when compared with the LOU rat, that elastin gene polymorphisms in these strains do not significantly account for. After a genome-wide search for quantitative trait loci (QTL) influencing the aortic elastin, collagen, and cell protein contents in an F2 population derived from BN and LOU rats, we identified on chromosomes 2 and 14, 3 QTL specifically controlling elastin levels, and a further highly significant QTL on chromosome 17 linked to the level of cell proteins. We also mapped 3 highly significant QTL linked to body weight (on chromosomes 1 and 3) and heart weight (on chromosome 1) in the cross. This study demonstrates the polygenic control of the content of key components of the arterial wall. Such information represents a first step in understanding possible mechanisms involved in dysregulation of these parameters in arterial pathology.

Animals↗

PubMed1985

On the possible relation of spreading cortical depression to classical migraine.

During the first 1 to 2 h of the classical migraine attack a hypoperfusion develops which starts in the posterior part of the brain and progresses anteriorly at a rate of 2-3 mm/min. The hypoperfusion stops at primary sulci outlining major cortical macro- and microstructural changes, but seems not to be inhibited by other changes of the cortical architecture. The low flow regions are cortical and the low flow persists for 4-6 h, until the attack abates. Regions of hyperperfusion are either minor or non-existent. A similar behavior characterizes the velocity and mode of evolution of a cortical spreading depression, a transient perturbation of cortical neuronal function which has profound and long-lasting influence on the cortical blood flow. This paper briefly summarizes the arguments which have been put forward in recent years suggesting that spreading depression is a pathogenetic mechanism of migraine.

Animals↗

PubMed1987

Application of expanded polytetrafluoroethylene (ePTFE) tubing to the study of human wound healing.

Wounds are a part of daily life. They range from minor nicks and cuts to the incisions of major surgery. In the sequence of evolution the process of healing arose long before modern science. The events which we are beginning to unravel have occurred routinely for a very long time despite our lack of understanding. We have learned how to nurture healing, but how to modify healing in a positive sense is only an approaching reality. Standardized tests of human healing are a necessary part of future research in wound healing. In the Wound Healing Laboratory we have used tubes of expanded polytetrafluoroethylene (ePTFE) as a tissue-sampling device in small, experimental, needle-stick wounds. Ingrowth into ePTFE is influenced by surface and structural characteristics. These are held constant, and "normal" values can be established and used as a base with which to study effects of various clinical states on healing in humans.

Biocompatible Materials↗

PubMed2006

Partial least square modeling of hydrolysis: analyzing the impacts of pH and acetate.

pH and volatile fatty acids both might affect the further hydrolysis of particulate solid waste, which is the limiting-step of anaerobic digestion. To clarify the individual effects of pH and volatile fatty acids, batch experiments were conducted at fixed pH value (pH 5-9) with or without acetate (20 g/L). The hydrolysis efficiencies of carbohydrate and protein were evaluated by carbon and nitrogen content of solids, amylase activity and proteinase activity. The trend of carbohydrate hydrolysis with pH was not affected by the addition of acetate, following the sequence of pH 7>pH 8>pH 9>pH 6>pH 5; but the inhibition of acetate (20 g/L) was obvious by 10%-60 %. The evolution of residual nitrogen showed that the effect of pH on protein hydrolysis was minor, while the acetate was seriously inhibitory especially at alkali condition by 45%-100 %. The relationship between the factors (pH and acetate) and the response variables was evaluated by partial least square modeling (PLS). The PLS analysis demonstrated that the hydrolysis of carbohydrate was both affected by pH and acetate, with pH the more important factor. Therefore, the inhibition by acetate on carbohydrate hydrolysis was mainly due to the corresponding decline of pH, but the presence of acetate species, while the acetate species was the absolutely important factor for the hydrolysis of protein.

Acetates↗

PubMedDate not supplied

[Otology in diseases of internal medicine interest].

Many clinical manifestations present signs of cochleovestibular impairment. In some cases, otological symptoms are a complication of a disease, while in other cases they are the only early signs and can last for a long period preceding the full development of the primary disease. The otological pathology in the former case is useful for investigating the internal pathology and sometimes for delivering correct diagnosis. On the contrary, in the latter case, it does not offer elements for any etiopathogenic hypothesis because it happens in almost all cases with an acute onset in an otherwise healthy subject and it is always underestimated because of the minor functional impairment. However, clinical studies in the last years led to a significant evolution of otological findings as an early important symptom in the etiopathogenic study and in the diagnosis of some internal diseases. This is true for connectivitis, in which the disease is often preceded by a sudden cochleovestibular symptom, in some dismetabolic or vascular diseases that sometimes begin with fluctuating hearing loss, or in some cochlear manifestations due to ototoxic origin.

Carboplatin↗

PubMed2005

The pelvic fin and girdle of Panderichthys and the origin of tetrapod locomotion.

One of the most marked transformations in the vertebrate transition to land was that of fins to limbs. This transformation involved not only the generation of morphological novelties (digits, sacrum) but also a shift in locomotory dominance from the pectoral to the pelvic appendage. Despite its importance, the transformation from pelvic fin to hindlimb is the least studied and least well-documented part of this transformation, which is bracketed by the osteolepiform Eusthenopteron and the early tetrapods Ichthyostega and Acanthostega, but is not directly illuminated by any intermediate form. Panderichthys is the closest tetrapod relative currently represented by complete fossils, but its pelvic fin skeleton has not been described. Here, I present the only known articulated pelvic fin endoskeleton and associated partial pelvis of Panderichthys. The pelvic girdle is even less tetrapod-like than that of the osteolepiform Eusthenopteron, but the pelvic fin endoskeleton shares derived characteristics with basal tetrapods despite being more primitive than the pectoral fin of Panderichthys. The evolution of tetrapod locomotion appears to have passed through a stage of body-flexion propulsion, in which the pelvic fins played a relatively minor anchoring part, before the emergence of hindlimb-powered propulsion in the interval between Panderichthys and Acanthostega.

Animals↗

PubMed1986

Platelets and foam cells in the evolution of atherosclerosis. Histological and immunohistological studies of human lesions.

Sixty-seven coronary, aortic and other lesions (39 subjects) ranging from minor to advanced disease were studied histologically and by immunohistology for antigens of platelets, beta-lipoprotein (LpB) and fibrinogen. Collections of lipid-filled foam cells were found in nearly every lesion mainly in the thickened intima, sometimes associated with macrophages. Foam cells were also present elsewhere including, in advanced lesions, necrotic zones filled with cholesterol needles. Then they too were necrotic. Platelets were observed in many lesions as small free clusters and/or phagocytosed in foam cells and sometimes also in macrophages. Cellular and extracellular reactions for platelet derivatives and for LpB were very frequent. Reactions for fibrinogen were only extracellular. Foam cell cytoplasm reacted for platelet derivatives and for LpB whilst macrophages, endothelium and certain other cells sometimes reacted for platelet derivatives but rarely for LpB. The studies indicate that: Foam cells originate from macrophages mainly in the intima and many migrate elsewhere. Their formation and their uptake of LpB requires cellular acquisition of a platelet factor or factors. Acquisition of platelet factor(s) is by phagocytosis of intact platelets and/or uptake of extracellular soluble derivatives from disrupted platelets. These processes begin early, are likely to be continuous and are significant for the evolution of atherosclerosis including the necrotic foci of advanced lesions.

Antigens↗